Add 32 most significant bits of gid key to key in btree mapping from

gid to lid in document meta store to reduce amount of CPU cache misses
during lookup.

1 files changed, 4 insertions, 0 deletions

diff --git a/document/src/vespa/document/base/globalid.h b/document/src/vespa/document/base/globalid.h
index ac30e189033..f84ce206093 100644
--- a/document/src/vespa/document/base/globalid.h
+++ b/document/src/vespa/document/base/globalid.h
@@ -81,6 +81,10 @@ public:
             value = ((value & 0x0f0f0f0f) << 4) | ((value & 0xf0f0f0f0) >> 4);
             return __builtin_bswap32(value);
         }
+        // Return most significant 32 bits of gid key
+        static uint32_t gid_key32(const GlobalId &gid) {
+            return bitswap(gid._gid._nums[0]);
+        }
 
         //These 2 compare methods are exposed only for testing
         static int compareRaw(unsigned char a, unsigned char b) {